Many types of flexible closures exist in the art of reclosable receptacles provided with such flexible closure means. Typically, such flexible closure means are made up of one strip of a male interlocking element and a second strip of a female interlocking element. The male and female elements together provide that which is commonly referred to as a mechanically interlocking closure. Examples of this type of closure are well known in the art including an interlocking closure available from Dow Chemical Company of Midland, Mich. sold under the trademark "Ziploc". Other examples are shown and described in U.S. Pat. Nos. 4,186,786 to Kirkpatrick, 3,198,228 to Naito and 3,780,781 to Uramoto.
In each of these references, a male interlocking strip is provided on one side of a flexible bag and a female interlocking strip is provided opposite to the male strip on an opposed side of the bag. The mouths of the bags are sealed closed by pressing the male and female closure strips against one another, causing macro-deformation of the male or female elements or both, until the elements are interfitted within one another and interengaged to seal the bag.
Another type of flexible closure material is available from Minnesota Mining and Manufacturing Company of St. Paul, Minn. which is described as an intermeshable article in U.S. Pat. No. 4,875,259 to Appeldorn, issued Oct. 24, 1989. Reference is also made to copending application Ser. No. 325,272 filed Mar. 22, 1989 describing such an intermeshable article specifically provided as an intermeshable closure for a container. In this intermeshable type of flexible closure, a plurality of strips of closure material having similar interengaging elements on each strip are interengaged with one another. Moreover, the flexible closure does not include any mechanical interlocking or macro-deformation of the interengaging elements. The closure material provides a receptacle seal similar to the mechanical interlocking types described above but which only requires intermeshing of the similar interengaging elements. The coefficient of friction of the strip material and the angle of the interengaging faces of the interengaging elements adequately provide a sealable receptacle closure. The terms interengaged and derivatives thereof as used throughout this application are meant to encompass both interlocking and intermeshing closure elements as distinguished from one another above.
No matter whether the interengaging closure system to be used is a mechanical interlocking type closure system or an intermeshing closure type system, it is imperative that the strips of flexible closure material be accurately aligned on the surfaces of the receptacle to be sealed and with respect to one another. Moreover accurately aligning the strips includes the step of affixing the closure strips, whether male and female closure strips or similar intermeshable element strips. Typically, the affixation is accomplished by heat sealing the strips of closure material to the receptacle material, such as a polymeric film in the case of a flexible plastic bag, with or without adhesive, or by extruding the male and female closure strips integrally with the film of the receptacle when the film is extruded.
An example of a reclosable bag including male and female closure strips extruded integrally with the film of the reclosable bag is disclosed in the above referenced U.S. Pat. No. 3,198,228 to Naito. Specifically, the closure elements are extruded with the film as a flat film which is folded intermediate of the closure elements along the longitudinal lengths thereof so that the closure strips align with one another to form the reclosable feature. This process requires an accurate folding of the film intermediate of the longitudinally extending closure strips such that accurate alignment of the strips to one another is accomplished. Moreover, the extrusion process controls the formation of the closure strips with respect to one another in parallel to one another. This process is significantly disadvantageous in that it is very difficult to change the positions of the closure strips on the bag, since any relocation thereof requires modification of the extruder head. Moreover, the process requires a specialized dedicated extruder for making the integral film and closure as opposed to using a conventional film extruder. Furthermore, the process disadvantageously requires very precise folding techniques in the bag formation step. All of these disadvantages increase the cost of production of such bags with reclosable closure means.
Otherwise, in order to bring separately extruded flexible closure strips to the receptacle material, such as film, it has been necessary to supply the two separate closure strips to the point of application and affixation of the closure strips to the receptacle material and bag formation. In this case, it can easily be understood that it is most important to accurately align the flexible closure strips on the opposed surfaces of the receptacle and with respect to one another. This being most difficult to do and requiring complex machinery. Moreover, separate supplies are required for each strip of closure material as well as for the receptacle forming material.
Another disadvantage associated with separately produced closure strips is that the process sometimes requires that the extruded flexible closure material be cut or trimmed into the relatively small width strip portions that are required to be applied to the receptacle. Typcially, the width of each closure strip is approximately one quarter inch or less. In the case of the intermeshable closure material described in the Appeldorn, U.S. Pat. No. 4,875,259, since the closure strips are similar to one another, it is sometimes necessary to cut or trim the closure strips down in size to the approximately one quarter inch or less before they can be applied to the receptacle. In this regard, it has been found to be increasingly difficult to size the closure material into decreasingly narrow strip portions. Moreover, during such cutting or trimming of the material in production, the outer edges of the strip portions may not be uniform. Specifically, the edges of the strip portions may vary side to side by a few grooves. This makes it even more difficult to align the interengaging elements of the strip portions on the receptacle with respect to one another.
Moreover, when dealing with plural separately produced and supplied strips of closure material (either interlocking or intermeshing), it is very unlikely that the plural strips would have been manufactured at the same time and under the exact same conditions. Thus, it is likely that the strips will be characterized by slightly different calipers and other qualities, which tends to make the alignment of the strips on a receptacle even more difficult.